Synchronizing system



Sept. 19, `1939.

F. G. NuxoLL Er AL SYNCHRONIZING SYSTEM Filed Feb. 9, 1937 gwuwvtoa JTNuzzoZL AJVLon,

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Patented Sept. 19, 1939 UNITED STATES PATENT OFFiCE SYNCHRONIZING SYSTEMApplication February 9, 1937, Serial No. 124,892

6 Claims.

This invention relates to synchronous communication systems andparticularly to high speed printing telegraph systems.

In the synchronizing systems in common use in high speed multiplextelegraphy, the rotary distributors at the transmitting and receivingstations are operated by a constant driving force, such as forkcontrolled motors of the La Cour type. It has been the practice toVoperate the distributor at the transmitting station, at the desiredsignal transmitting speed and the distributor at the receiving stationat a slightly greater speed. A corrector mechanism which operates inconjunction with the receiving distributor maintains the brushes of thedistributors in proper phase relation by stepping the brushes of thereceiving distributor backward, independently of the driving motor,Whenever an angular shift between the brushes and the motor shaft wasrequired in order to restore said proper phase relation. This method ofmaintaining the phase relation between the brushes of the respectivedistributors is disclosed in Patent No. 1,298,622 granted to Yorke andBenjamin, March 25, 1919. In this system each current reversal affectingthe correcting relay affords an opportunity for making a correction; butthe correction mechanism operates only when, at the time of one or moreof such reversals, the brushes of one distributor are suiciently out ofphase with the brushes of the other distributor to require correction,

Due to irregularities and distortion in the shape of the receivedsigna-l wave, which may be caused by extraneous currents, variations inline characteristics etc., the instants of reversal may varyconsiderably from the theoretically correct point so that the brush maybe suiciently out of phase to require a succession of correctingimpulses to restore it. It is evident therefore that there is an area ofuncertainty in which the point of current reversal may occur.

As the brushes of the receiving distributor are driven at a slightlygreater speed than those oi the transmitting distributor, they have atendency to gain in phase with respect to the brushes at thetransmitting station. This causes a slow creep of the area ofuncertainty over the corrector segments in the direction oi brushrotation. As the area of uncertainty tends to creep onto the nextforward segment, it will only be able to reach a position such that theproportion of the area that extends over the advance segment will justcontain the number of reversals necessary to effect the requiredretardation and it Will hunt back and forth as the control mechanismattempts to hold that portion of it -necessary for compensation over thesegment.

The phase wander inherent in the above correction methods prohibitstheir use in extremely high speed signaling systems when the signalimpulse waves become very short. Moreover the relays which actuate thecorrecting device require relatively large impulses thus making itnecessary for a considerable arc to pass between the brush and segmentbefore the contact area be'- tween brush and segment becomes largeenough to pass sufficient current to operate a relay.

One purpose of my invention is to provide a corrector system whichfollows the mean position of a series of signal current reversals andthus is controlled by the phase relation between the average receivedreversals and the corrector ring, thereby overcoming the tendency tohunt and the irregularity of the prior edge correction devices.

'I'he synchronizing system disclosed herein is an improvement upon thesystem described and illustrated in said Yorke and Benjamin Patent No.1,298,622, in which the rotary distributors at the transmitting andreceiving stations are driven by fork controlled La Cour motors, thebrushes of the receiving distributor (designated as the "correcteddstributor) being driven at a slightly greater speed. The brushes of thecorrected distributor are stepped backwardly independently of thedriving motor in the manner illustrated in Fig. 1c of said patent,whenever the angular shift between the brush and the motor shaft isrequired to restore proper phase relation between the brushes of the twodistributors. The disclosure of said patent is assumed to be embodied inthis case.

The accompanying drawing is a diagram illustrating the circuitarrangement of our improve-- ment in synchronizing systems.

The control mechanism of the phase corrector embodies a segmented ringconsisting of pairs of segments A and B, the corresponding segments ofeach pair being connected together. In the usual correcting system, inwhich the brush of the corrected distributor is retarded to effect acorrection, if the distributor brush is rotated in synchronism with thesignals, each reversal Will occur While the brush is on one of the Asegments. In this event no correction will be applied. However, if thedistributor brush gains relative to the rate of signal transmission, sothat a reversal occurs while the brush is on one of the B segments, acorrecting impulse is produced which actuates the magnet of thecorrector mechanism to set the brush back, relative to the driving motorshaft so as to restore it to the proper A segment.

Referring to the accompanying drawing, the corrector relay l receivestheincoming signals. Its armature is connected to a grounded condenserCo of small capacity, which picks up a positive charge from thecorrector rings 2, while the corrector relay is on its marking contact,if the corrector brush is on a B segment at that instant, the amount ofthis charge being determined by the phase relation between the signalreversal and the corrector brush 3 at the instant the corrector relayleaves its marking contact. The pick-up condenser Cu discharges into alarger storing condenser C1 while the corrector relay is on its spacingcontact, thereby producing an increment or decrement in the voltage ofstoring condenser C1, the magnitude of which is dependent on the ratioof the two capacities. The function of the resistance Ro is to preventcondenser Co from completely discharging between successive reversalswhen the signal frequency is low, thus making the eiTect or" a singlereversal dependent upon the number of correcting opportunities afforded.

If we assume storing condenser C1 to be discharged, it is evident thatif the phase relation of the signal reversals to the position of thecorrector b-rush 3 is such that a preponderance of positive incrementsare received, condenser C1 will gradually acquire a positive charge at arate depending upon the number of positive increments per unit of timeand therefore upon the phase relation between the received signal andthe corrector ring.

For the purpose of interpreting this potential rise in terms of thephase correction required. per unit of time, a normally deenergizedneutral relay 5, pro-vided with tongues and l, is connected to oneelectrode or" a negative glow lamp or neon tube N, the other electrodebeing under the control of the potential across storing condenser C1. Asthe potential of condenser C1 becomes more positive, a potential isreached which causes the gaseous ionizable gap of the neon tube to breakdown, thus permitting a sudden rush or surge of current to flow throughthe neutral relay. The operation of the relay causes a short circuitthrough tongue C5 to be placed around the neon lamp, thus permitting adirect discharge of the condenser C1 to prolong the impulse through theneutral relay and ensuring a sufficient operating pulse. Simultaneouslycurrent from positive battery through relay tongue 'I operates themagnet 8 of the mechanical corrector and causes the corrector brush 3 tostep backward. When the potential across condenser C1 has been reducedto a certain value, current through the neutral relay will beinsufficient to hold the relay tongues in operated position so that theywill return to the unoperated position. This removes the short ,circuitacross the neon lamp and permits the sto-ring condenser C1 to againacquire a positive charge in the manner previously described.

The voltage across the neon lamp is now below the ionizing or breakdownpoint so that it is evident that the above described functions will berepeated at a rate which is determined by the rate of rise of potentialacross condenser C1 and therefore by the phase relation between theaverage received reversal and the correcting ring.

By connecting a leak resistance R1 from condenser C1 to positivebattery, the condenser can be charged at such a rate that the correctormechanism will be operated periodically at the average rate when currentreversals fail to arrive for a number of revolutions of the distributoror in case of a momentary failure of the line and thereby step thecorrector brush to maintain synchronism with the distributor at thetransmitting station.

In order to be able to step the brushes backward quickly to bring thebrushes into proper phase relation after an interruption a switch buttonl is provided in a normally open shunt circuit, provided with a suitableresistance R3, to lower the resistance between the condenser C'1 andresistance R5, thereby causing the corrector mechanism to operate at afaster rate than the normal rate.

As noted above, in the Yorke-Benjamin synchronizing system the correctormechanism follows the edge of the correcting area, whereas in theintegrating or averaging corrector system disclosed herein, thecorrector follows the mean of a series of signal current reversals.'Ihis results in overcoming the tendency to hunt and the irregularity inthe corrector movements of the prior devices.

We claim:

l. A synchronizing system for telegraph apparatus, comprising a signalreceiving relay, a condenser proportionally arranged to storeincremental charges controlled by said relay, tary member normally inphase With said signals, a corrector magnet operable under control of asurge of said condenser as the rotary member tends to move out of phase,mechanical means including said magnet for correcting the position ofsaid rotary member, and insulating means between the condenser and saidmagnet which becomes conductive at a certain potential to thereby permitsaid condenser surge when the condenser charge attains said potential.

2. A synchronizing system for telegraph apparatus, comprising adistributor, a brush cooperating therewith, means for rotating saidbrush, mechanical means for changing the angular displacement of saidbrush With respect to said distributor, a polar relay, a condenserproportionally arranged to store incremental charges upon they operationof said relay on the receipt of signals of one polarity, said mechanicalmeans being operated to step said brush by a surge of said condenser andan ionizable gaseous path between the condenser and the relay permittingthe passage of said surge at a certain potential.

3. In a synchronizing system for telegraph apparatus, a distributor, abrush moving thereover, a polar signal receiving relay, a pick-upcondenser of small capacity, said condenser being charged through oneContact and discharged through the other contact of said relay, a secondstoring condenser of larger capacity, said second condenser beingproportionally arranged to be increasingly charged by the successivedischarges of said first named condenser, means operable by a surge ofsaid second condenser to cause angular displacement of said brush withrespect to the distributor, and an ionizable device arranged to breakdown at a certain potential to thereby control the instant at which saidsurge occurs.

4. In a synchronizing system as set forth in claim 3, means actuated bysaid surge to short circuit said ionizable device and thereby facilitateand prolong discharge of the condenser.

5. In a synchronizing system as set forth in claim 3, an auxiliarycircuit connecting said second condenser with a potential source togradually charge said second condenser and cause a periodical surgetherefrom during a temporary interruption in the received telegraphsignals.

6. In a synchronizing system as set forth in claim 3, and means formanually connecting a potential source to said second condenser toproduce a desired number of condenser surges for the purpose of quicklyobtaining the desired angular displacement of said brush.

FREDERICK G. NUXOLL. PAUL A. NOXON.

